Volume 4 completes the documentary record of Washington's first year as commander in chief of the Continental army. It opens with his final preparations to leave Cambridge following the successful siege of Boston and concludes with news that General William Howe's British army was soon to arrive at New York, an event that would mark the beginning of the New York campaign. In the interim between campiagns, Washington established his headquarters at New York and began wrestling with the perplexing problems of defensing the strategically important corridor between New York and Canada formed by the Hudson River and Lake Champlain.

Throughout the spring of 1776, Washington faced a choice of difficulties in allotting the scarce military resources at his disposal. Long uncertain of British intentions for the coming campaign, he felt obliged to strengthen both ends of the Hudson-Champlain corridor. In April Washington seriously depleted his army at New York by sending two large detachments of Continental troops to reinforce the weak and dispirited American forces in Canada. At the same time he pushed vigorously to complete fortifications in and around New York City and in the Hudson highlands. A continuing shortage of men and arms, rumors of Loyalist conspiracies, and discipline problems aggravated by the exposure of young soldiers to urban vices added to his burdens during this time. In late May Washington went to Philadelphia to consult with the Continental Congress for the first time since commissioning in June 1775. His discussions of strategy with the delegates resulted in a series of resolutions on which Washinton was to base many of his decisions in the troubled days ahead. In a personal sense the trip to Philadelphia was significant because Martha Washington, who accompanied the general to the city, was innoculated successfully for smallpox during her stay, freeing her to continue traveling with her husband without fear of contracting that dreaded disease. After an absence of more than two weeks, Washington returned to his New York headquarters in early June to resume preparations for what he frankly told his brother Jack would be "a very bloody Summer."